System for remotely securing/locking a stolen wireless device via an Email message

ABSTRACT

A system for remotely securing or locking a wireless information device is provided by sending an Email message with an attached password to the device. The owner of an information device specifies a password and a security level beforehand. The specified information is stored in a memory. When an electronic mail is received from another information device through a wireless telephone facility of the information device, a password attached to the electronic mail is checked with the password stored in the memory. When the password match occurs, a security process corresponding to the security level stored in the memory is executed. Security processes include processes of display screen lock, owner indication, and data erase. Thus, in the case where the information device should be lost or stolen, the leakage of data to others can be prevented.

BACKGROUND OF THE INVENTION

The present invention relates to an information device having a securityfacility that provides the protection of data against unauthorizedaccess by others and a method therefor, and more specifically to aportable information device that permits communications of electronicmail with no mail server involved and a method for providing thesecurity of data.

In recent years, electronic mail by personal computers and wordprocessors has spread rapidly to companies and individuals. In order fora company or an individual to employ electronic mail, it is required toinstall a host computer adapted for electronic mail in the company orjoin a commercial electronic mail service (personal computercommunications service such as NIFTY Serve, or the like).

In the conventional electronic mail systems, mail (character stringdata) to be interchanged between information devices is stored in thebulk storage of an in-company electronic mail computer, called a mailserver, or a commercial electronic mail service computer. Both thesender and the receiver make access to (call) the mail server mainly viatelephone lines.

FIG. 1 shows a conventional electronic mail system. In the conventionalsystem, information devices, such as personal digital assistants (PDAs),interchange mail via a mail server 2.

As an example, to send mail data from the information device 1a to theinformation device 1b, the information device 1a first makes access tothe mail server 2 and then sends the mail data addressed to theinformation device 1b to the mail server 2. The information device 1blikewise makes access to the mail server and receives from the mailserver the mail data addressed to it.

As described above, a mail server (computer) adapted to store andinterchange mail data is dispensable for the conventional electronicmail system. That is, mail interchange between information devicescannot be achieved without making access to the mail server. Thus, itcannot be said that the conventional electronic mail system can beemployed easily by anyone. For this reason, an implementation of asimple electronic mail system has been desired which, unlike theconventional electronic mail system, allows mail interchange amonginformation devices with no mail server involved.

FIG. 2 shows an arrangement of such a simple electronic mail system.Information devices 10a, 10b and 10c each have a digital telephonefacility built in. Each of the information devices is equipped with afacility for directly sending or receiving electronic mail to or fromanother information device. In this case, information devices can beused which have a built-in wireless telephone facility such as thepersonal handyphone system (PHS) which is a digital simplified telephonesystem adopted in Japan. With such an arrangement, electronic mail canbe interchanged among the information devices 10a, 10b and 10c freelywith no mail server involved.

If the simplified electronic mail system as shown in FIG. 2 is used inplace of the conventional electronic mail system shown in FIG. 1, thenmail data, which, in the conventional system, are managed by the mailserver, will be managed by individual information devices. In this case,there will arise the following problems.

In the simplified electronic mail system, mail data are held onindividual information devices. In case where the owner of aninformation device should leave it somewhere or he or she should have itstolen, there arises the possibility that another person may use it toknow mail data. In this case, even if the owner is aware that theinformation device has been missing, he or she cannot take anycountermeasures against it.

To solve the problem of data leakage to others, a method for securitywill be conceived which sets information devices to demand of each userthe entry of a password each time he or she activates his or herinformation device to thereby allow data to be made open only toauthorized users. With this method, however, users who have to activateand stop their information device over and over again a day will feeltroublesome for an operation of entering a password each time theyactivate it. For this reason, it cannot be said that it is preferable touse such a method.

BRIEF SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide aninformation device which permits the prevention of data from beingleaked out to others when it is missing, with no need of entering apassword or the like in the normal use of it and a security methodtherefor.

According to an aspect of the present invention, there is provided aninformation device for a wireless communication with a network thatallows transmission and reception of electronic mails, comprising: meansfor storing a password; means for storing a security level; means forchecking a password attached to an electronic mail with the passwordstored by the password storing means in response to the reception of theelectronic mail from the network; and security process execution meansfor, when the password match occurs, executing a security processcorresponding to the security level stored by the security level storingmeans.

According to another aspect of the present invention, there is providedan information device for a wireless communication with a network thatallows transmission and reception of electronic mails, comprising: meansfor performing an editing operation of inserting into an electronic mailto be transmitted a password adapted to allow another information deviceto perform a security process in it; and means for transmitting theelectronic mail into which the password has been inserted to the anotherinformation device.

According to still another aspect of the present invention, there isprovided an electronic mail system having first and second informationdevices for a wireless communication with a network that allowstransmission and reception of electronic mails, the first informationdevice comprising: means for storing a password; means for storing asecurity level; means for checking a password attached to an electronicmail with the password stored by the password storing means in responseto the reception of the electronic mail from the network; and means for,when the password match occurs, executing a security processcorresponding to the security level stored by the security level storingmeans; and the second information device comprising: means forperforming an editing operation of inserting into an electronic mail tobe transmitted a password adapted to allow the first information deviceto perform the security process in it; and means for transmitting theelectronic mail into which the password has been inserted to the secondinformation device.

According to a further aspect of the present invention, there isprovided a method of implementing security for an information devicehaving a wireless telephone facility that allows transmission andreception of electronic mails, comprising the steps of: storing aspecified password and security level into a memory; checking a passwordattached to an electronic mail with the password stored in the memory inresponse to the reception of the electronic mail from the network; andwhen the password match occurs, executing a security processcorresponding to the security level stored in the memory.

According to another aspect of the present invention, there is provideda method of implementing security for a first information device for awireless communication with a network that allows transmission andreception of electronic mails, comprising the steps of: on the side of asecond information device, performing an editing operation of insertinginto an electronic mail to be transmitted a password adapted to allowthe first information device to perform a security process in it; andtransmitting the electronic mail into which the password has beeninserted to the first information device.

According to still another aspect of the present invention, there isprovided a method of implementing security for a first informationdevice for a wireless communication with a network that allowstransmission and reception of electronic mails, comprising the steps of:on the side of the first information device, storing a specifiedpassword and security level in a memory; on the side of a secondinformation device, performing an editing operation of inserting apassword into an electronic mail to be transmitted; transmitting theelectronic mail into which the password has been inserted from thesecond information device to the first information device; on the sideof the first information device, checking the password in the electronicmail with the password stored in the memory in response to the receptionof the electronic mail from the network; and on the side of the firstinformation device, executing a security process corresponding to thesecurity level stored in the memory.

According to a further aspect of the present invention, there isprovided a storage medium having program code instructions storedthereon which are readable by an information device for a wirelesscommunication with a network that allows transmission and reception ofelectronic mails, the instructions comprising: when a password and asecurity level are specified, storing the contents thereof in a memory;checking a password attached to an electronic mail with the passwordstored in the memory in response to the reception of the electronic mailfrom the network; and when the password match occurs, executing asecurity process corresponding to the security level stored in thememory.

Additional objects and advantages of the present invention will be setforth in the description which follows, and in part will be obvious fromthe description, or may be learned by practice of the present invention.The objects and advantages of the present invention may be realized andobtained by means of the instrumentalities and combinations particularlypointed out in the appended claims.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate presently preferred embodiment ofthe present invention and, together with the general description givenabove and the detailed description of the preferred embodiment givenbelow, serve to explain the principles of the present invention inwhich:

FIG. 1 is a schematic illustration of a conventional electronic mailsystem;

FIG. 2 is a schematic illustration of a new electronic mail system;

FIG. 3 is a block diagram of a hardware implementation of an informationdevice according to an embodiment of the present invention;

FIG. 4 is a perspective view of the information device of FIG. 3;

FIG. 5 is a schematic illustration of facilities of the informationdevice of FIG. 3;

FIG. 6 is a schematic illustration of security settings on the LCD ofthe information device of FIG. 3;

FIG. 7 shows data communications between information devices of FIG. 3;

FIG. 8 shows the form of a password to be sent by the information deviceof FIG. 3;

FIG. 9 is a flowchart for the password transmission procedure of theinformation device of FIG. 3;

FIG. 10 is a flowchart for an operation of receiving data of theinformation device of FIG. 3;

FIG. 11 is a flowchart for security processing of the information deviceof FIG. 3;

FIG. 12 is a flowchart for owner indication processing of theinformation device of FIG. 3;

FIG. 13 is a flowchart for screen lock processing of the informationdevice of FIG. 3; and

FIG. 14 is a flowchart for data erase processing of the informationdevice of FIG. 3.

DETAILED DESCRIPTION OF THE INVENTION

A preferred embodiment of the present invention will now be describedwith reference to the accompanying drawings.

Referring now to FIG. 3, there is illustrated in block diagram form ahardware implementation of an information device according to anembodiment of the present invention. This information device is aportable information device that has a wireless telephone facility suchas the PHS which is one of digital simplified telephone systems and hasbeen adopted in Japan. The wireless telephone facility allows not onlytransmission and reception of usual voice data but also transmission andreception of mail data in the format of MIME (Multipurpose Internet MailExtensions) or mail data based on personal computer communicationsservices such as NIFTY-Serve and the like.

In FIG. 3, reference numeral 11 denotes a micro processing unit (MPU)that controls the entire information device.

Reference numeral 12 denotes a ROM which is used as fixed storage andstores program codes, a dictionary for kana-to-kanji translation, etc.In addition, the ROM 12 has a security program storage area 12a storedwith a security program and also stores a PIM (Personal InformationManager) 21, which will be described later with reference to FIG. 5, andsoftware for a telephone facility section 22.

Reference numeral 13 denotes a RAM used as main storage, in whichvarious items of data are stored for processing by the MPU 11. Inaddition, the RAM 13 has a password storage area 13a for storing apassword (which will be described later) that is specified by theinformation device owner, a security level storage area 13b for storinga security level (to be described later) that is likewise specified bythe information device owner, and buffer areas for INBOX 23 and OUTBOX24 which will be described with reference to FIG. 5.

The password stored in the storage area 13a differs in nature from thepassword used in the conventional system and is used in case ofemergency where the information device is lost or stolen. That is, thepassword stored in the storage area 13a is used to check a passwordindicating a security processing instruction when it is sent fromanother information device.

Reference numeral 14 denotes an infrared communications unit for datainterchange with another information device. Reference numeral 15denotes a PC card interface unit adapted for PCMCIA, which makes varioustypes of PC cards available. Reference numeral 16 denotes a tablet forpen-based data entry. Reference numeral 17 denotes a liquid crystaldisplay (LCD) for displaying the contents of electronic mail that issent or received, and so on.

Reference numeral 18 denotes a wireless telephone unit forsending/receiving voice data or mail data by radio. Reference numeral 19denotes a light emitting diode (LED) for indicating that electronic mailor the like is being received.

FIG. 4 is a perspective view of the portable information device.

Reference numeral 51 denotes a power button that is used to turn theinformation device on and off. Reference numeral 52 denotes an antennawhich is used to send or receive voice data or mail data. Referencenumeral 53 denotes a loudspeaker which, when the telephone facility isimplemented, reproduces voice of the user at the station with which theconnection has been set up. Reference numeral 54 denotes a microphonewhich, when the telephone facility is implemented, picks up user'svoice. Reference numeral 55 denotes a pen which is used to writecharacters and figures on the tablet 16 for data entry. Referencenumeral 56 denotes a cursor key which is used to make a choice fromvarious items displayed on the LCD 17. Reference numeral 57 denotes atelephone button which is used in implementing the telephone facility.Reference numeral 58 denotes a talking button which is used for talkingthrough the telephone facility.

FIG. 5 shows functions of the information device. In addition to the PIM21 having personal information manage functions such as a schedule book,address book, notepad, etc., the information device has the digitaltelephone facility 22 added or built in. It should be noted here thatthe telephone facility can be added by the use of a PC card as anexample.

The telephone facility allows mail data as well as usual voice data tobe transmitted/received. In this case, mail data received from anotherinformation device is stored in the INBOX 23 serving as an input buffer.On the other hand, mail data created by the notepad function in the PIM21 for transmission to another information device is stored in theOUTBOX 24 serving as an output buffer.

To facilitate the understanding of the present invention, a simplifiedelectronic mail system used in the embodiment will be described withreference to FIG. 2.

In FIG. 2, the information devices 10a, 10b and 10c comprise thesimplified electronic mail system. As described previously, eachinformation device has a built-in function of directly transmitting orreceiving mail data to or from an information device at the other end.Unlike the conventional system shown in FIG. 1, therefore, thesimplified electronic mail system allows mail data to be interchangedamong the information devices 10a, 10b and 10c with no mail serverinvolved.

The mail data transmitting/receiving function in the telephone facility22 can be performed independently of the other functions. Even if, whenthe information device is placed in the mail data receive state, it isoperated by the user, mail data sent from another information devicewill be received automatically and then stored in the INBOX 23. When theuser later terminates the operation and confirms that electronic mailhas been received, he or she can immediately watch mail data in theINBOX 23 on the screen of the LCD 17.

In the case of mail transmissions, on the other hand, the user createsmail data online using the notepad function in the PIM installed in theinformation device, chooses a recipient or recipients using thetelephone directory function, then places the mail data into the OUTBOX24, so that the mail data is placed in the wait state for transmission.

When several items of mail data have been stored, the mail sendingfunction is activated and the state of connection with anotherinformation device is confirmed. If transmission is possible, the itemsof mail data (waiting mail) in the OUTBOX 24 are automatically sent insequence to the another information device. Later, the user can know themail data transmission conditions by examining the OUTBOX 24. If an itemof mail data which has not been sent is found, it can be retransmittedautomatically to the corresponding information device.

The simplified electronic mail system can be combined with theconventional mail-server-based electronic mail system, which will allowelectronic mail to be employed more flexibly.

FIG. 6 shows the security setting screen of the information device ofthe invention. To provide against the information device being lost orstolen, the owner specifies a password and a security process in advanceon the security setting screen of the LCD 17 as shown in FIG. 6.

As shown in FIG. 6, a password entry field 31 is set up on the securitysetting screen. The password entry field can accommodate a password ofeight digits for example. The owner enters a desired password into thatfield through the tablet 16. This password is used for the owner toactivate the security facility of the information device from a remotelocation in case of emergency. The information device has a built-infunction of checking a password attached to mail data sent from anotherinformation device. The function is performed certainly when mail dataincluding the password is received and cannot be stopped by a personusing the information device.

In addition, security levels 32, 33 and 34 are set up on the securitysetting screen. Here, "owner indication" is set as the security level32, "screen lock" as the security level 33, and "data erase" as thesecurity level 34. The information device owner makes a choice fromamong these security levels.

Here, "owner indication" means the display of data that identifies theinformation device owner, such as name, telephone number, or the like,on the LCD 17, "screen lock" means the prohibition of data display onthe LCD 17, and "data erase" means the erasing of all data theinformation device holds or erasing of data that have been specifiedbeforehand as candidates for erasing.

The password information specified on the security setting screen isstored in the password storage area 13a of the RAM 13. The informationabout the chosen security level is stored in the security level storagearea 13b of the RAM 13.

In the security program storage area 12a of the ROM 12 there has beenstored beforehand a program that executes the security processcorresponding to the previously specified security level when a passwordsent from another information device matches the password specifiedbeforehand by the owner. Since this program is set up on the ROM, itcannot be altered or erased by a person using the information device.

The security processing will be described next.

Here, the processing will be described in terms of information devices41 and 42 adapted to transmit/receive mail data for the purpose ofsimplifying the description. It is assumed here that the owner of theinformation device 42 has left it somewhere and hence operates it fromthe remote information device 41 so that the security processing will beperformed. In this case, the information device 42 becomes an object ofsecurity. When a predetermined password is sent from the informationdevice 41 to the information device 42, the security processing isperformed on the receiving side.

Before describing the operation of the information devices, a techniqueof sending a password from the information device 41 to the informationdevice 42 will be described.

In this embodiment, a password can be transmitted in a message headerdefined by the MIME that is the Internet electronic mail standard. Thatis, as shown in FIG. 8, a password is inserted into a header fielddefined by the MIME as its subject. In this case, the password isdescribed in the form of encoded binary data although it is not shown indetail in FIG. 8. The use of such a technique allows a password to betransferred between the information devices 41 and 42 that support theMIME.

FIG. 9 illustrates a process flow of the information device 42 at thetime of receiving data.

The owner of the information device 42 activates a function of editingtransmit mail based on the MIME on the other information device 41 (stepA11). The owner of the information device 42 causes the screen forediting the header field defined by the MIME to appear on the LCD (stepA12). The owner then fills in a password in the form of binary data intothe subject field as shown in FIG. 8 (step A13). The password to befilled in must match the password that has been previously set up by theowner on the information device 42.

After the password has been filled in, the owner of the informationdevice 42 sends mail data containing that password to the informationdevice 41 (step A14).

FIG. 10 is a process flow of the information device 42 at the time ofreceiving data. It is assumed that the owner of the information device42 that is now an object of security has already specified the passwordand the security level on it through the security setting screen asshown in FIG. 6. Upon receiving data sent from the information device 41to the information device 42, the MPU 11 of the information device 42performs the following processing.

That is, the MPU 11 first makes a decision as to whether or not data(calling packet) sent from the information device 41 to the telephonefacility section 22 of the information device 42 has been sent byelectronic mail (step B11). The calling packet contains identificationinformation adapted to distinguish between mail data and voice data. Bydetermining the identification information, the MPU can know whether theinformation device 42 was called by telephone or by electronic mail.

In the case of calling by telephone (not by electronic mail) (NO in stepB11), the MPU 11 produces a ringing tone through the wireless telephoneunit 18 (step B12) and places the telephone facility section 22 in thetalking state (step B13).

In the case of calling by electronic mail (YES in step B11), on theother hand, the MPU 11 receives mail data via the wireless telephoneunit 18 (step B14). The received mail data is temporarily stored in abuffer storage.

The MPU 11 then determines whether or not a password is attached to themail data stored in the buffer (step B15). If no password is attached(NO in step B15), then the MPU 11 retains the mail data in the INBOX 23as normal mail data (step B17).

The MPU 11 next makes access to the OUTBOX 24 to determine whether ornot mail data to be send to another information device is present (stepB18). This mail data has been created by the use of the notepad functionof the PIM 21. In the presence of such mail data (YES in step B18), theMPU 11 sends it to that location via the wireless telephone unit 18(step B19) and then disconnects the telephone line to enter the readystate (step B20). In the absence of such mail data (NO in step B18), onthe other hand, the MPU disconnects immediately the telephone line toenter the ready state (step B20).

That is, when mail data ready for transmission to a location is present(i.e., when mail data is present in the OUTBOX 24), it can be sentautomatically to the location upon receiving electronic mail from thesame location. More specifically, if, when mail data 41a is sent fromthe information device 41 to the information device 42, mail data 42aaddressed to the information device 41 is held in the information device42, the mail data 42a can be sent to the information device 41 while theconnection between the information devices 41 and 42 is beingestablished. Conversely, if, when a location sends mail data, thereceiving location holds ready mail addressed to that sending location,the sending location can also receive that mail data addressed to it.

If a password is attached to mail data (YES in step B15), but it doesnot match the password that is stored in the password storage area 13aof the RAM 13 (NO in step B16), then it is retained as normal mail datain the INBOX 23.

If, on the other hand, a password is attached to mail data (YES in stepB15), and it matches the password stored in the password storage area23a (YES in step B16), then the MPU 11 carries out the securityprocessing corresponding to the specified security level (step B21).

The security processing in step B21 will be described in detail withreference to a flowchart of FIG. 11.

That is, the MPU 11 starts a security program stored in the securityprogram storage area 12a of the ROM 12 (step C11). As a result, thesecurity program refers to the security level storage area 13b of theRAM 13 to identify the security level specified by the owner (step C12)and then carries out the security processing corresponding to thesecurity level.

When the "owner indication" as the security level 32 is specified inFIG. 6 (YES in step C13), the MPU 11 performs the owner indicationprocess (step C14). When the "screen lock" as the security level 33 isspecified (YES in step C15), the MPU 11 performs the screen lock process(step C16). When the "data erase" as the security level 34 is specified(YES in step C17), the MPU 11 performs the data erase process (stepC18).

Specifically, in the case of the owner indication process, the MPU 11displays on the LCD 17 data that identifies the information deviceowner, such as name, telephone number, or the like. The data to identifythe owner has been previously entered into the RAM 13 by the owner. Incase where the owner left the information device 42 somewhere, someonemight contact the owner.

When the "screen lock" is specified as the security level, the MPU 11prohibits the display of data on the LCD 17. This will make itimpossible for others to see user data held in the information device42. To cancel the screen lock, use is made of a cancel password, whichmay be the same as that used in the screen lock process or may beanother password.

When the data erase process is specified, the MPU 11 erases all userdata held in the information device 42, or erases data that has beenspecified beforehand as a candidate for erasing. This allows theprevention of leakage of secret data to others in case the where theinformation device 42 should be stolen.

Next, specific procedures for the owner indication process, the screenlock process, and the data erase process will be described withreference to flowcharts of FIGS. 12, 13 and 14.

In the owner indication process of FIG. 12, the name or telephone numberthat has been entered beforehand by the user is read from the RAM 13(step D11). The name or telephone number read is displayed on the LCD 17(step D12).

In the screen lock process of FIG. 13, the LCD screen is cleared (stepE11). The tablet 16 is next locked so that entry of data from the pen(input device) is ignored (step E12).

In the data erase process of FIG. 14, all the information stored in theuser's data area in the RAM 13 is erased (step F11).

In a simplified electronic mail system which allows mail data to beinterchanged between information devices with no mail server involved,since the owner can activate the security facility in his or herinformation device from a distance, data leakage to others can beprevented even if the information device should be lost or stolen.

Although the embodiment of the present invention was described as usinga telephone line as the communication path, any other communicationspath that allows direct communications can be used to transmit/receiveelectronic mail. For example, slave phone-to-slave phone communicationin the PHS can also be used for electronic mail.

The technique of the present invention described above can be applied tovarious types of devices in the form of a computer program constitutedby program code instructions by writing it into a storage medium, suchas a magnetic disk (floppy disk, hard disk, or the like), optical disk(CD-ROM, DVD, or the like), or semiconductor memory, or transmitting itover a communication medium. Information devices that implement thepresent system read the computer program recorded on a storage mediumand run it to thereby perform the above-described process.

According to the present invention, as described above, a simplifiedelectronic mail system that allows mail interchange between informationdevices with no mail server involved is provided. This electronic mailsystem allows an information device to perform a security function, suchas owner indication, display screen lock, or data erase, by causing theowner of that information device to specify beforehand a password to beused and a security function to be performed in case of emergency and,in the case where that information device should be lost or stolen,allowing the owner to send the password to that information device fromanother information device. Thereby, the leakage of user data held inthe information device to others can be prevented even if theinformation device should be lost or stolen.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the present invention in its broaderaspects is not limited to the specific details, representative devices,and illustrated examples shown and described herein. Accordingly,various modifications may be made without departing from the spirit orscope of the general inventive concept as defined by the appended claimsand their equivalents.

I claim:
 1. An information device for a wireless communication with a network that allows transmission and reception of electronic mails, comprising:means for storing a password; means for storing a security level; means for checking a password attached to an electronic mail with the password stored by the password storing means in response to the reception of the electronic mail from the network; and security process execution means for, when the password match occurs, executing a security process corresponding to the security level stored by the security level storing means.
 2. The information device according to claim 1, wherein the security level indicates that the display of data held in the information device should prohibited.
 3. The information device according to claim 1, wherein the security level indicates that information indicating the owner of the information device should be displayed.
 4. The information device according to claim 1, wherein the security level indicates that user data held in the information device should be erased.
 5. The information device according to claim 1, further comprising:means for specifying the password to be stored by the password storing means; and means for specifying the security level to be stored by the security level storing means.
 6. The information device according to claim 1, wherein the security process execution means has a security processing program for performing the security process.
 7. The information device according to claim 1, wherein the information device is equipped with a wireless telephone facility.
 8. An information device for a wireless communication with a network that allows transmission and reception of electronic mails, comprising:a first memory for storing a password; a second memory for storing a security level; a processor for checking a password attached to an electronic mail with the password stored in the first memory in response to the reception of the electronic mail from the network, and when the password match occurs, executing a security process corresponding to the security level stored in the second memory.
 9. An information device for a wireless communication with a network that allows transmission and reception of electronic mails, comprising:means for performing an editing operation of inserting into an electronic mail to be transmitted a password adapted to allow another information device to perform a security process corresponding to a security level stored in advance in said another information device and means for transmitting the electronic mail into which the password has been inserted to the another information device.
 10. The information device according to claim 9, wherein the password is inserted in the form of binary data into the header field of the electronic mail.
 11. An electronic mail system having first and second information devices for a wireless communication with a network that allows transmission and reception of electronic mails,the first information device comprising: means for storing a password; means for storing a security level; means for checking a password attached to an electronic mail with the password stored by the password storing means in response to the reception of the electronic mail from the network; and means for, when the password match occurs, executing a security process corresponding to the security level stored by the security level storing means; and the second information device comprising: means for performing an editing operation of inserting into an electronic mail to be transmitted a password adapted to allow the first information device to perform the security process in it; and means for transmitting the electronic mail into which the password has been inserted to the second information device.
 12. A method of implementing security for an information device having a wireless telephone facility that allows transmission and reception of electronic mails, comprising the steps of:storing a specified password and security level into a memory; checking a password attached to an electronic mail with the password stored in the memory in response to the reception of the electronic mail from the network; and when the password match occurs, executing a security process corresponding to the security level stored in the memory.
 13. The method according to claim 12, wherein the security level indicates that the display of user data held in the information device should prohibited.
 14. The method according to claim 12, wherein the security level indicates that information indicating the owner of the information device should be displayed.
 15. The method according to claim 12, wherein the security level indicates that user data held in the information device should be erased.
 16. The method according to claim 12, further comprising the steps of:specifying the password to be stored in the memory; and specifying the security level to be stored in the memory.
 17. The method according to claim 12, wherein the security process is performed by a security processing program.
 18. The method according to claim 12, wherein the information device is equipped with a wireless telephone facility.
 19. A method of implementing security for a first information device for a wireless communication with a network that allows transmission and reception of electronic mails, comprising the steps of:on the side of a second information device, performing an editing operation of inserting into an electronic mail to be transmitted a password adapted to allow the first information device to perform a security process corresponding to a security level stored in advance in said another information device and transmitting the electronic mail into which the password has been inserted to the first information device.
 20. The method according to claim 19, wherein the password is inserted in the form of binary data into the header field of the electronic mail.
 21. A method of implementing security for a first information device for a wireless communication with a network that allows transmission and reception of electronic mails, comprising the steps of:on the side of the first information device, storing a specified password and security level in a memory; on the side of a second information device, performing an editing operation of inserting a password into an electronic mail to be transmitted; transmitting the electronic mail into which the password has been inserted from the second information device to the first information device; on the side of the first information device, checking the password in the electronic mail with the password stored in the memory in response to the reception of the electronic mail from the network; and on the side of the first information device, executing a security process corresponding to the security level stored in the memory.
 22. A storage medium having program code instructions stored thereon which are readable by an information device for a wireless communication with a network that allows transmission and reception of electronic mails, the instructions comprising:when a password and a security level are specified, storing the contents thereof in a memory; checking a password attached to an electronic mail with the password stored in the memory in response to the reception of the electronic mail from the network; and when the password match occurs, executing a security process corresponding to the security level stored in the memory. 